In 2000 Yo-Yo Ma, long fascinated with cross-cultural exchange, assembled the Silk Road Ensemble--a leap from his classical perch that has broadened both his artistry and the world of music. The group now has a shifting roster of more than 50 members and a large repertoire of new commissions, traditional music from countries along the ancient Eurasian trade routes, and Western classical compositions. Ma sees the project as a musical conversation rather than a fusion of styles, Western instruments playing side by side with Eastern ancestors such as the pipa and the sheng, a Chinese mouth organ. This is the first major event of Silk Road Chicago, a yearlong partnership, and it includes three compositions from the group's most recent CD, Silk Road Journeys: Beyond the Horizon--"Gallop of a Thousand Horses," Persian folk melodies using the rhythm of horse hooves; "Yanzi," a Kazakh song in a soulful Chinese arrangement for cello and voice; and "Tarang," a dialogue between Western strings and Eastern percussion. Ma will be joined by, among others, virtuosos Wu Tong (sheng) and Yang Wei (pipa). The Chicago Symphony Orchestra Brass Quartet will open the concert with selections from Gabrieli's Venetian Canzoni. Mon 6/26, 6:30 PM, Pritzker Pavilion, Millennium Park, 100 N. Michigan, 312-742-1168. Free.